docs: add build cache

.github/workflows/rust.yaml

@@ -74,20 +74,44 @@ jobs:
     - name: Run docs
       run: cargo doc --workspace --all-features --no-deps --document-private-items --verbose
 
-    - name: Install mdBook and mdBook-Mermaid
+
+        
+    - name: Cache mdbook installation
+      uses: actions/cache@v2
+      with:
+        path: ~/.cargo/bin/mdbook
+        key: ${{ runner.os }}-mdbook
+
+    - name: Cache mdbook-mermaid installation
+      uses: actions/cache@v2
+      with:
+        path: ~/.cargo/bin/mdbook
+        key: ${{ runner.os }}-mdbook-mermaid
+
+    - name: Install mdBook if not installed already
       run: |
-        cargo install mdbook
-        cargo install mdbook-mermaid
-        mdbook-mermaid install ./docs/
+        if [ ! -f ~/.cargo/bin/mdbook ]; then
+          cargo install mdbook
+        fi
+
+    - name: Install mdBook-mermaid if not installed already
+      run: |
+        if [ ! -f ~/.cargo/bin/mdbook-mermaid ]; then
+          cargo install mdbook-mermaid
+        fi
 
     - name: Cache mdBook build
-      id: cache-mdbook
+      id: mdbook-build-cache
       uses: actions/cache@v3
       with:
-        path: path/to/your/book/book-output
-        key: ${{ runner.os }}-mdbook-${{ hashFiles('path/to/your/book/**') }}
+        path: ./docs/book/
+        key: ${{ runner.os }}-mdbook-${{ hashFiles('./docs/**') }}
         restore-keys: |
           ${{ runner.os }}-mdbook-
 
     - name: Build the book
-      run: mdbook build /docs/
+      run: mdbook build ./docs/
+
+    - name: Build the book
+      if: steps.mdbook-build-cache.outputs.cache-hit != 'true'
+      run: mdbook build ./docs/